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T Yanagida

Publications and source records attributed to T Yanagida.

At least 163 records · Page 9Linked to original sources
PubMed1987

Microelectrode depth study of the electroretinographic oscillatory potentials in the frog retina.

The depth profile of the electroretinographic oscillatory potentials was studied in the isolated frog retina. The intraretinal electrode was introduced from the receptor side, and the reference electrode was placed on the vitreal side. The electroretinogram, recorded either transretinally or with the electrode tip in the receptor layer, showed 4 to 10 oscillatory potential wavelets. As the electrode was advanced proximally, the wavelets disappeared as a function of retinal depth. The wavelets with longer peak latencies disappeared earlier, and only the first one or two wavelets could be identified when the electrode was in the inner plexiform layer. These findings indicate that the oscillatory potentials are generated between the inner and outer plexiform layers and that the earlier wavelets originate in the more proximal retina. The results are consistent with the notion that the oscillatory potentials are generated by synaptic feedback circuits.

Animals↗
PubMed1986

Suppression of the hyperosmolarity response after cataract surgery.

The hyperosmolarity response was recorded with the electrooculogram in the dark before and after cataract extraction, to investigate a possible disorder in the retinal pigment epithelium after cataract extraction. The hyperosmolarity response was suppressed one week after surgery, especially after intracapsular extraction. The response recovered up to the preoperative level in most cases one or two months after surgery. These findings indicate reversible functional disorders of the pigment epithelium after cataract extraction, particularly intracapsular. This dysfunction can be revealed by the hyperosmolarity response. This response is clinically useful for diagnosis of pigment epitheliopathy after cataract extraction.

Adult↗
PubMed1986

Roles of lysine1 and lysine7 residues of bovine pancreatic ribonuclease in the enzymatic activity.

In order to investigate the roles of Lys1 and Lys7 of RNase A in the enzymatic activity, four S-peptide derivatives were prepared and their abilities to activate S-protein were measured. They are 1-norleucine-S-peptide, 7-norleucine S-peptide, 1,7-di-norleucine-S-peptide, and tri-N-acetyl S-peptide. From the analyses of the relative activity and kinetic parameters of RNase S' derivatives with UpU, UpU greater than p, and UpUpU greater than p, it was concluded that Lys7 of RNase A is a binding site for 3'-phosphate of UpU greater than p and the modification or substitution of Lys1 affects the binding of trinucleotide substrate.

Animals↗
PubMed1986

Microelectrode depth study of electroretinographic b- and d-waves in frog retina.

The depth profiles of the b- and d-waves of the electroretinogram were studied in the isolated frog retina placed with its receptor side up. The electrode was introduced into the retina from the receptor side and the reference electrode was placed on the vitreal side. The b-wave was maximum in amplitude in the receptor layer, and decreased as the electrode was advanced proximally from the outer plexiform layer until it disappeared at the inner limiting membrane. The b-wave in the inner plexiform layer was different from that in the distal portion of the inner nuclear layer in form and peak latency. The results suggested that the b-wave is generated in the layers between the inner limiting membrane and the outer plexiform layer, and that at least two processes are involved in the generation of the b-wave. The depth profile of the d-wave resembled that of the b-wave except in the receptor layer; it was recorded in the whole retinal layers as was the b-wave, and decreased as the electrode was advanced proximally until it disappeared at the inner limiting membrane. The peak latency of the d-wave was longer in the inner plexiform layer than in the distal portion of the inner nuclear layer. The results indicated that the d-wave consists of the off-response of the late receptor potential and the postsynaptic components, the latter being generated by a similar mechanism as the b-wave.

Animals↗
PubMed1985

Angle of active site of myosin heads in contracting muscle during sudden length changes.

The change in orientation of myosin crossbridges in contracting muscle during sudden length changes was examined by fluorescence polarization. This study used a fluorescent ATP analogue, 1,N6-etheno-2-aza-ATP(epsilon-2-aza-ATP) as a probe. Its fluorescence is considerably enhanced upon binding with myosin and is dependent on the chemical state of the myosin-nucleotide complex in muscle. The results showed that nucleotides bound to crossbridges in the intermediate attached state (presumably AM-epsilon-2-aza-ADP-Pi) during isometric contraction are highly oriented at the same angle as that of AM in rigor with bound epsilon-2-aza-ADP. Furthermore the orientation of nucleotides bound to crossbridges in the attached state is not altered during sudden changes in length of isometrically contracting muscle. The results of this time-resolved measurement support the conclusion obtained from a previous steady-state experiment that change in axial orientation of the active site of the myosin head is not involved in force generation.

Animals↗
PubMed1984

Predominant attached state of myosin cross-bridges during contraction and relaxation at low ionic strength.

The chemical states of a cross-bridge--nucleotide complex were studied using a fluorescent ATP analogue, 1-N6-etheno-2-aza-ATP(epsilon-2-aza-ATP). The fluorescence of epsilon-2-aza-ATP at specific emission wavelengths was enhanced by 12.5 times upon binding to myosin in a relaxed muscle and the fluorescence from the resultant myosin(M)-epsilon-2-aza-ADP-Pi intermediate was 2.5 times greater than that from a M-epsilon-2-aza-ADP complex. Similar enhancements of the fluorescence of epsilon-2-aza-ATP and epsilon-2-aza-ADP were observed upon binding to heavy meromyosin in solution. Binding of F-actin did not change the fluorescence of epsilon-2-aza-ATP or epsilon-2-aza-ADP bound to heavy meromyosin. When a muscle went from a relaxed state to a state of isometric contraction or contraction with shortening, the fluorescence intensity decreased only slightly or not at all, i.e. the fluorescence of nucleotides bound to most of the myosin heads during contraction is the same as that of the M-epsilon-2-aza-ADP-Pi intermediate. These results suggest that an actomyosin(AM)-epsilon-2-aza-ADP-Pi intermediate is the predominant attached state during contraction. When the ionic strength of the relaxing solution was decreased, cross-bridges formed at 6 degrees C without tension generation. At 20 degrees C, a large tension was produced although the shortening velocity was negligibly small or zero. The fluorescence intensity decreased by 15% at 20 degrees C but only a small decrease of 3% was observed at 6 degrees C, suggesting that the predominant complexes in the attached state were AM-epsilon-2-aza-ATP and/or AM-2-aza-ADP-Pi at 6 degrees C and AM-epsilon-2-aza-ADP at 20 degrees C. Thus, the identification of the actomyosin-nucleotide complexes existing before and after the force-generating step lent further support to the conclusion that the sliding force is generated by conformational changes in actomyosin when the (epsilon-2-aza-)ADP-Pi complex is bound to it.

Adenosine Diphosphate↗
PubMed1984

Angles of fluorescently labelled myosin heads and actin monomers in contracting and rigor stained muscle fiber.

The measurement of polarized fluorescence from a fluorescent ATP or ADP analog, epsilon-ATP or epsilon-ADP (1, N6-Etheno-ATP or ADP) bound to myosin heads in a glycerinated muscle fiber revealed that during isometric contraction at low concentrations of Mg-epsilon-ATP the bound nucleotides are highly oriented with respect to the fiber axis, and their mean angle is almost the same as that in rigor. Furthermore, the polarization of tryptophan fluorescence did not change when the fiber was transferred from a rigor state to an active state at low ATP concentrations. Thus, if a rotation of myosin heads occurs during contraction, it seems to be very limited. The angle of bound epsilon-ADP is not changed by passive stretching of the fiber in the presence of epsilon-ADP. By using the same technique, it was found that orientation of a phalloidin-FITC complex (Ph-FITC) specifically bound to F-actin in a glycerinated muscle fiber is significantly changed when the fiber is activated from relaxation or rigor to contraction. No change in orientation of Ph-FITC bound to F-actin is induced by simple addition of Mg-ADP or by passive stretching of the fiber in the absence of ATP. These results suggest that a rotation or a distortion of actin monomers occurs during contraction, which is involved in the process of active tension development.

Actins↗
PubMed1984

Asymmetrical potassium permeability of the Müller cell. Field potential induced by intraretinal injection of K+-free Ringer's in frog retina.

The field potentials induced by intraretinal injection of K+-free Ringer's were studied in the isolated frog retina. The response to K+-free Ringer's was a positive potential, which was maximum near the depth of injection, and decreased in both directions, proximally and distally. The receptor side was made positive relative to the vitreal side, irrespective of the depth of injection, excepting for the innermost retinal layer bordering the inner limiting membrane. The response at the site of injection and the transretinal potential were dependent upon the depth of injection, being largest when the K+-free Ringer's was injected in or near the inner plexiform layer. Thus, the field potentials induced by K+-free Ringer's were similar in depth profile but opposite in polarity to those induced by high K+-Ringer's. The results were consistent with the previous conclusion that the proximal end region of the Müller cell is far more permeable to K+ than any other part of the cell.

Animals↗
PubMed1984

[The clinical significance of tissue polypeptide antigen (TPA) in the patients with gynecologic tumor].

In order to estimate the clinical significance of tissue polypeptide antigen (TPA), TPA was measured by radioimmunoassay in sera from patients with various gynecological tumors. They were 40 uterine myomas, 94 cervical cancers, 21 endometrial cancers, 3 vulval cancers, 51 benign ovarian tumors and 78 malignant ovarian tumors including 18 low potential malignant tumors (LPM). The mean TPA values in patients with benign as well as malignant tumors were significantly higher than that of 97 healthy volunteers (68 +/- 17 U/l; Upper limit; 107 U/l). Among the cervical cancer patients, serum TPA level and positive ratio became higher as the disease progressed. In the advanced cases, the mean serum TPA value and positive ratio were 149 +/- 64 U/l and 75%, respectively. The mean TPA value in the endometrial cancer patients was significantly higher than that of myoma patients. Among the patients with ovarian tumor, serum TPA was elevated in 14% of benign cases, 28% of LPM cases, 47% of stage I cases and 82% of the advanced cases. Serum TPA values varied directly with the stage and malignancy of disease. The present study revealed that TPA is a useful markers in the diagnosis of gynecological tumors, especially for ovarian cancers.

Adenocarcinoma↗